How are Parkinson's disease and ALS similar? Both diseases are preventable.
Dementia is a symptom of both diseases.
Both diseases affect control of voluntary muscles.
Scientists understand the causes for both diseases.

HELP PLZ

Both diseases affect the control of voluntary muscles.

Explanation:

Parkinson's disease is a progressive brain disease that affects movement. It affects the nerve cells that produce dopamine in the part of the brain called substantia nigra. The symptoms include shaking, stiffness, and difficulty with walking, balance, and coordination. Symptoms get worse with time, often leaving people with difficulty walking and talking.

ALS (amyotrophic lateral sclerosis) is a progressive nervous system disease that affects nerve cells in the brain and spinal cord. The first symptoms usually involve muscle weakness, and as the disease progresses, it results in the loss of muscle control.

Scientists don't know the exact cause of these diseases. As the cause is not known, there is no exact way to prevent them. There is no cure for them, either. The treatment is focused on the management of symptoms.

This is why the third option is the correct one.